Hey guys, through another thread I was working on with the expert community here, and quite a bit of research, I've been able to design this circuit with the hardware I have available that fits the needs for running what I need.
NOTE: The picture represents the solenoid as a motor, and the second relay as a smaller relay than it is. But the other thread describes the actual hardware I'm using.
The GRM-8 relay, is a 12-250v relay, that needs about 2.5 amps to energize and fire the coil. It's triggered through a signal on the S line, and powered on A1 and A2. It receives 12 volts through a power supply.
The Transistor I'm using is an NPN and an EBC - for ease of reading.
I don't fully understand the circuit in a few places, maybe with the critiques, I can ask some questions, like what is the purpose of the DIODE between the collector and the relay?
Here's the diagrams, thank you for your help everyone, I'd love to know how I can make it efficient, and safe for the hardware, and people.
Also: I know I can simplify this circuit considerably using a MOSFET, which looks awesome, so I'm ordering some. I'm sure I'll be back with more questions.
Can somebody tell me how to get the circuit diagram in reasonable contrast (b/w?) on my Linux Mint with Firefox? The green wires and labels are almost invisible on my screen
Really? That's pretty substantial for a Relay. (I couldn't find any definitive spec sheet for a "GMR8 relay")
You probably don't want to run 2.5A for the relay plus whatever the solenoid takes through a breadboard!
Running the 1st stage relay off of 3.3V seems like a bad idea; the 3.3V supply on an Arduino is typically pretty weak compared to the 5V supply.
The solenoid and the GMR8 relay should probably have diodes as well. And at those current levels, perhaps snubber circuits (unless those are built in.)
I use it as a CAD (Computer Aided Design) program for schematic capture. It runs great on Linux, also available for other platforms but I have no experience on them.
At that stage it shouldn't matter really if I use the 5v or the 3.3 volt side right? I just picked one and moved forward, so it's not any educated decision.
Here's some actual pictures of the setup. They're a little messy, but may help a bit to advise me of all the things I've done wrong.
I use a diode across A1 and A2 in the case of the relay. Stripe towards A2.
I use nothing on the Solenoid itself. It's sitting lonely over there on the right side of the picture, the SNS device. It's a pretty substantial relay, meant to work under PSI up to 60 or 120 I think, I'd have to look it up.
It might be easier to see now. The circuit actually works, but that doesn't mean they aren't backwards. Are they?
Also, to clarify. The solenoid (represented by the "motor" in the picture) is the 2.5 amps to hold open, (and 2.6 to activate). The GRM8-01 takes about 60ma to activate at the absolute lowest, measured with my bench supply, and my fluke in series with its signal. Which is still 3 times what the microcontroller can handle over GPIO, hence the 5 volt relay between.
I'd love to know if the transistor I have 2n2222 could fire the GRM8 directly, everything I tried didn't work.
The 1k base resistor limits base current to about 4mA, and that limits safe collector currrent to less than 100mA. Change that base resistor to 220 ohm. Then a 2N2222 might survive up to 500mA collector current. A logic level power fet would be a much better solution.
Leo..
Right. It needs somewhere along the lines of 10 volts or so, to show up on the S line to trigger the relay. In practice that means shorting S and A1 together with 12 volts on that line, and a mA flow of about 100mA average.
I'm looking into a MOSFET that can fire the solenoid directly, or at least fire the latching relay that fires the solenoid, any advice on this?
1.) Should I fire the relay using a MOSFET, or eliminate the relay all together and fire the solenoid directly?
2.) What type of device should I use to accomplish number 1? I know a MOSFET, but I don't know MOSFETS, so which one?
Ok, that sounds like something I should know...how come? Different voltage tolerance on the pins?
And also, am I reading the stat sheet correctly? The IRLZ44N can handle 47A continuous current? Would that be at 12 volts, or there's a calculation I need to know?
